The present invention relates generally to blood monitoring devices, and, more particularly, to a lancing mechanism for lancing a user""s skin to obtain a sample of blood for analysis.
It is often necessary to quickly obtain a sample of blood and perform an analysis of the blood sample. Preferably, the obtaining of blood is as painless as possible. One example of a need for painlessly obtaining a sample of blood is in connection with a blood glucose monitoring system where a user must frequently use the system to monitor the user""s blood glucose level.
Those who have irregular blood glucose concentration levels are medically required to regularly self-monitor their blood glucose concentration level. An irregular blood glucose level can be brought on by a variety of reasons including illness such as diabetes. The purpose of monitoring the blood glucose concentration level is to determine the blood glucose concentration level and then to take corrective action, based upon whether the level is too high or too low, to bring the level back within a normal range. The failure to take corrective action can have serious implications. When blood glucose levels drop too lowxe2x80x94a condition known as hypoglycemiaxe2x80x94a person can become nervous, shaky, and confused. That person""s judgment may become impaired and that person may eventually pass out. A person can also become very ill if their blood glucose level becomes too highxe2x80x94a condition known as hyperglycemia. Both conditions, hypoglycemia and hyperglycemia, are both potentially life-threatening emergencies.
One method of monitoring a person""s blood glucose level is with a portable, hand-held blood glucose testing device. The portable nature of these devices enables the users to conveniently test their blood glucose levels wherever the user may be. In order to check the blood glucose level, a drop of blood is obtained from the fingertip using a separate lancing device. The lancing device contains a needle lance to puncture the skin. Once the requisite amount of blood is produced on the fingertip, the blood is harvested using the blood glucose testing device. The blood is drawn inside of the testing device which then determines the concentration of glucose in the blood. The results of the test are communicated to the user via a display on the testing device.
Many prior art lancing devices implement a spring coupled to the actual lance to move the lance to its penetration depth. The lance is drawn back to compress the spring. When released, the spring extends thus forwardly propelling the lance to its penetration depth. One problem associated with some prior art lancing devices is that the penetration depth of those lances is dependant on a spring constant which is a measure of the spring""s stiffness. The mechanical qualities of a spring, including the stiffness, tend to degrade over time with use. Accordingly, over time, the penetration depth of many prior art lances may vary. When the penetration depth of the lance lessens over time, the lance may not produce a laceration deep enough to draw the requisite volume of blood necessary for blood glucose analysis. An insufficient lancing can result in an erroneous analysis if the user does not recognize that the lancing has not produced the requisite volume of blood for analysis. Or, if the user does recognize an insufficient lancing has occurred, the user must re-lance resulting in another laceration in the user""s skin and more pain. The user may eventually have to replace the lance which has degraded over time.
Another related problem associated with many of the aforementioned prior art lancing devices is that when the spring forwardly advances the lance to its penetration depth, the spring extends past its static length. The spring then retracts the lance; however, due to the oscillatory nature of the spring, the lance is retracted past its static length. The lance continues to oscillate in this manner thus entering the laceration created in the user""s skin several times. Put another way, with each actuation of a prior art lancing device, a user""s skin is lanced several times which results in a larger laceration. A larger laceration in the user""s skin translates into more pain for the user and a longer time for the laceration to heal.
Accordingly, there exists a need for a lancing mechanism which moves a lance a known stroke not dependent on a spring constant and the extension of the spring past its static length.
A lancing mechanism for puncturing skin is provided. The lancing mechanism comprises a lance having a penetration end which is adapted to puncture skin. The penetration end of the lance is movable from a first position to a second position during a forward stroke and between the second position and the first position during a return stroke. A forcing plunger applies a force to the lance to move the lance from the first position to the second during the forward stroke. The forcing plunger is adapted to engage the lance during the forward stroke to move the penetration end of the lance from the first position to the second position and to disengage the lance when the penetration end of the lance approaches the second position. A first resilient member coupled to the lance moves the first end of the lance from the second position to the first position during the return stroke.
The above summary of the present invention is not intended to represent each embodiment, or every aspect, of the present invention. Additional features and benefits of the present invention will become apparent from the detailed description, figures, and claims set forth below.